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We reconstructed vegetation changes and fire events in the southern Lake Baikal region over the past 33 cal kyr using a sediment core from the Buguldeika Saddle, southern Lake Baikal, to examine vegetation response to past short-term climate variations. Herbs, such as Artemisia and Asteraceae, were dominant just before the Last Glacial Maximum (LGM). Low pollen accumulation rates (PARs) with little herb pollen indicate sparse herbaceous vegetation cover during the LGM. Picea expanded after the Bolling interval, suggesting expansion of riparian areas, and shrub Alnus rapidly increased during the following Allerod interval. Abies and Pinus subgen. Haploxylon began to increase at the beginning of the Holocene and Pinus subgen. Diploxylon has been highly dominant since the middle Holocene. The vegetation change after the LGM is similar to that from other sites in the Lake Baikal region, but the responses to short-term climate events are pronounced. Fluctuations in herb elements and vegetation cover as indicated by the PAR correspond to the Younger Dryas (YD) cooling event. The decline in the PAR and increase in herb taxa were remarkable at the beginning of the YD, but Larix and Picea trees were distributed in river valleys near Lake Baikal in the latter half. The rapid expansion of Betula and Artemisia following frequent fires in the early Holocene may have been in response to the 8.2 cal ka BP cooling event. From these findings, the southern Lake Baikal region, including the Selenga River basin, may possibly have been more sensitive than other parts of the region to abrupt climate changes.

To better understand the response of forest vegetation to climate and fire regimes with reference to human activities over the last deglacial period in the Aso Caldera, central Kyushu, southwestern Japan, a 33.9 m long sediment core was examined in order to reconstruct the vegetational and fire history using pollen and charcoal analyses. The results show that a cool temperate broad-leaved deciduous forest, dominated by Quercus (deciduous oaks) with Carpinus and Fagus, prevailed in the Aso Valley from ca. 14.6 ka cal. b.p., indicating warming since the last glacial period. The landscape was presumably covered by a mosaic of deciduous Quercus forests and terrestrial Artemisia communities. Around 12.8–11.7 ka cal. b.p., Quercus dominated the forest and fires occurred frequently. Co-expansion of distinctive Ulmus–Zelkova and Celtis–Aphananthe forests coupled with a progressive retreat of Quercus in the early Holocene could reflect a strengthening of the East Asian summer monsoon under mild and humid climate conditions. Around 8 ka cal. b.p., significant increases in Cyclobalanopsis (evergreen oaks), Castanopsis/Castanea and Podocarpus indicate a further warming, in particular an increased winter temperature. Warm temperate lucidophyllous forests, dominated by Cyclobalanopsis, flourished after 7.3 ka cal. b.p., probably corresponding to the “Holocene Climatic Optimum” interval. Progressive expansion of Quercus at the expense of Cyclobalanopsis began around 6.4 ka cal. b.p. and paralleled an increase in charcoal until ca. 4.8 ka cal. b.p.; this could be evidence of fire disturbance induced by the early-middle Jomon people. The disturbed evergreen forest experienced a temporary recovery but then opened again from 3.6 ka cal. b.p. due to extensive fire deforestation, as suggested by the high charcoal levels during this time. Human exploitation and buckwheat (Fagopyrum) agriculture may have contributed to the opening of the forest, which allowed secondary forests (primarily Pinus and Quercus) and herbaceous communities (mainly Poaceae) to spread. These results are discussed in comparison with other high-resolution pollen data from western Japan to better elucidate the vegetation and fire history over the last deglacial in the Aso Caldera.

A flight of Holocene marine terraces on the southwestern coast of Cape Omaezaki of central Japan provides evidence of recurrent millennium-scale uplift events. We reconstructed the uplift history of these terraces by using facies analysis of drill core and geoslicer samples, environmental analysis of trace fossils, and 14C age determinations. Coastal uplift can be identified by the displacement of beach deposits such as foreshore deposits, which represent the intertidal swash zone of a wave-dominated sandy coast. Three levels of former beach deposits facing the Nankai Trough were identified near the coast in the Omaezaki area. The highest of these, dated at about 3020–2880 BC, records a maximum of 2.2–2.7 m of emergence. The middle beach surface, of minimum age 370–190 BC, shows 1.6–2.8 m of emergence. The lowest beach surface, which is older than 1300–1370 AD, records 0.4–1.6 m of emergence. Our analysis of vertical crustal deformation data during the Holocene in this region suggests that rapid and strong uplift was restricted to the southwestern coast of the Omaezaki area and was probably caused by high-angle thrusting on subsidiary faults branching from the underlying plate boundary megathrust.

Aso valley (Asodani) is the northern part of Aso Caldera crater which made by depression after the forth of Aso pyroclastic eruptions, also has a floor of 470-500m altitude, that is surrounded by 350-500m high caldera rim at the north, and the central Aso volcano is situated at the south. The upper part of bottom sediments of Asodani is mainly composed sand, silt and clay in the main area, in which a wide fan spreads on the eastern floor and a meander river plane om the midstream of Kuro river (Kurokawa) on the western one. The under parts of sloop beside of the caldera rim are often formed by gravel and coarse materials from the cliff. Formations in the midstream of Kurokawa started deposition as a gravel bed formed by stream on the bottom of the valley during in the late period of the Last Glacial Age, and deposited silt and clay in a lake during 21,000 to 8,800 yBP. After 8,800 yBP, the deposition of Kurokawa started again in the area and the sedimentary environment is continuing to today. On the other hand, it is assumed that fan deposition has continued on the eastern part of Asodani after the Last Glacial Age.

(2008). Paleoenvironmental record of Lake Hovsgol (Mongolia) in northeast Eurasia. SIL Proceedings, 1922-2010: Vol. 30, No. 2, pp. 318-322.

We conducted particle size and pollen analyses on two cores extracted from Lake Baikal to investigate the response of vegetation to climate change and to assess the differences in vegetation changes between the northern and southern regions of Lake Baikal over the last 350 kyr. Vegetation changes in the Lake Baikal region corresponded well to the fluctuations in median particle size, which are indicators of the climate changes in this region. Forest, which was mainly composed of Pinus and Picea, spread widely during the interglacials/interstadials of MIS 9, 7, 5, and 1, and open forest or desert covered most areas during the glacial/stadial substages. However, the responses of vegetation to climate changes differed between the northern and southern regions. Generally, vegetation expansion was restricted around the northern region. During the interglacial substages equivalent to MIS 9.3, 7.5, and 5.5, forest spread widely around both the northern and southern regions. However, sparsely vegetated (poor) desert/open forest covered the northern region during MIS 5.3 and 5.1, while forest extended around the southern region in these substages. Moreover, during glacial periods, open forest, composed mainly of Artemisia, Chenopodiaceae/Amarantaceae, Betula, and Alnus, covered the southern region, while poor desert/open forest covered the northern region. These different vegetation responses are considered to have been caused by the geographical characteristics of the regions, i.e., the mountains around the northern region and the plains around the Selenga River in the southern region.

Submarine sediments in Ariake Bay, Kyushu Japan, were examined to assess geoenvironmental changes in the area. 6 core samples from representative stations (Stas. 1-6) were analyzed for 16 minor elements (S, Cl, Ba, Rb, Th, Nb, Zr, Y, Ga, V, Zn, Cu, Ni, Co, Cr, and Pb) using XRF. Based on measurements of 210Pb radioactivity, sedimentation rates at 2 stations, one off the Chikugo River (Sta. 2) and the other at the mouth of Isahaya Bay (Sta. 4), were calculated, respectively, at 0.24 cm/year and a maximum of 0.15 cm/year.The concentrations of heavy metals, such as Cr, Ni, Zn, and Pb, in the marine sediments are about one-third of those of the highly polluted marine sediments recorded in Tokyo Bay around 1970. The vertical profile of a minor element can be divided into an upper section and a lower section. The upper section indicates various gradual changes, but the lower section is almost constant. The boundaries between the sections roughly correspond to the beginning of the 20th century, based on the sedimentation rate.Zn and Pb in the submarine sediments can be useful indicators to trace suspended mud derived from the Chikugo River. The complementary relationship of the vertical profiles in the spatial distribution suggests that the continuous migration of the sedimentary province may be governed by the geometrical arrangement of the estuaries of major rivers and by the tidal circulation pattern in Ariake Bay. Probably, large dams built on the major rivers have hampered the sedimentation process dominated by traction flow and have decreased the maximum drainage speed. As a result, such processes have promoted the expansion of the muddy area in Ariake Bay.Planktonic dinoflagellata (Sta. 2) and diatom (Sta. 4) fossils were also analyzed. Assuming such sedimentation rates at the stations, marine phytoplanktons (Brigantedinium spp., Rhizosorenia spp. and Skeletonema costatum), which indicate eutrophication of the sea water, have increased in relative abundance during the past 10 years.

バイカル湖の湖底から得られた5.1Maをカバーする全長200mコア(BDP96-1)のうち,第四紀に相当する上部の深度80m以浅についての花粉分析を行い,植生変遷について考察した.産出した化石花粉・胞子のうち51種類を同定したが,マツ科針葉樹が70～80%を占め,その産出状況に特色がみられた.すなわち,大量の化石花粉・胞子の産出する多産層(間氷期,湿潤期)と,草本花粉・胞子がごくわずかに産出するだけの稀産層(氷期,乾燥期)が交互に現れている.上部80mの2Maに32回のサイクルが認められ,δ18O曲線とほぼ調和的な環境変動を記録している.また,マツ科のツガ属と落葉広葉樹のクマシデ属,コナラ亜属,クリ属,ニレ科,ハシバミ属,カエデ属は第四紀前半に絶滅してしまい,後半以降のバイカル湖周辺のタイガはマツ科針葉樹とカバノキ属を中心とした比較的単純な植生からなる森林が継続した.

Accelerator mass spectrometry (AMS) radiocarbon dating and paleoecological analysis of slope deposits at Mt Raizan provided seven 14C dates indicating that landslides occurred in that area at 6.0 to 6.3 cal ka BP and 6.5 cal ka BP. Plant macrofossils, pollen grains, and spores point to a mixed forest at that time, consisting of conifers and broad-leaved trees. On the other hand, insect fossil indicates slightly colder climate than that of the flora. This difference may be attributed to varied sensitivities of each proxy to climatic changes.

有明海周辺では,Aso-4火砕流堆積物の下位に最終間氷期の堆積物が存在することが報告されている.筆者らは,熊本平野の地下でAso-3火砕流堆積物とAso-4火砕流堆積物の間に,貝化石を産する細粒部を含む堆積物を見い出し,御幸層と命名した.御幸層の層相は,下部の砂礫層,中部の砂礫を含むシルト層,上部の砂礫層と変化している.また,御幸層は,Aso-3火砕流堆積物とAso-4火砕流堆積物の堆積時期から,12万年前から8万年前に堆積したと考えられ,最終間氷期で関東の小原台期にあたる.さらに,御幸層中部の上面深度と堆積時期から,最終間氷期以降の平均沈降速度が熊本平野の地域ごとに求められた.すなわち,沈降速度は熊本平野の東側にあたる御幸付近では0.45mm/年,海岸部近くでは0.90mm/年であり,平野西部へいくほど沈降速度が速くなっていることが明らかになった.

A palynological study was conducted on samples taken from the bottom sediments of Lake Baikal. The pollen records from 600-m to 400-m depth of the BDP-98 core show that the vegetation consisted mainly of broad-leaved tree forests composed of Fagaceae, Ulmaceae, and Juglandaceae in the lower part of the core. In the middle and upper parts of the core, the vegetation consisted mainly of coniferous tree forests and deciduous broad-leaved tree forests. The coniferous tree forests were composed of Pinus and Picea accompanied by Tsuga and Larix, and the deciduous broad-leaved tree forests were mainly composed of Betula and Alnus. A major reduction in palynological diversity and abundance was found at 8.6 Ma. In addition, a drastic change in the Steppe/forest index (SFI; Traverse 1988) was detected, reflecting the intensification of dry conditions. After the change, Betula and Alnus became more important elements of the deciduous broad-leaved tree forests, suggesting that a cool continental climate prevailed.

There is no large lake, such as Lake Baikal or Lake Hovsgol, in the Tunka depression now, but it is one of the depressions of the Baikal rift zone. The bottom of the depression is formed of Miocene to Holocene rocks set on Precambrian and Paleozoic rocks, which mainly crop out in mountains north and south of the depression. In Miocene times, lacustrine sediments were formed and basaltic lava flows erupted. However, in the Pliocene and Pleistocene, fluvial or fluvioglacial sediments were formed. Therefore, it is assumed that the development of the Tunka depression is different from that of Lake Baikal and Lake Hovsgol. The difference has to do with the outflow of water via the Irkut river during the Phocene, Pleistocene, and Holocene. In the Phocene, any large lake apparently disappeared, because the sediments are composed of coarse sand and pebbles produced by the rivers. In the Pleistocene, many gravel beds were formed by fluvial and fluvioglacial processes, and, especially in the middle Pleistocene, water probably flowed out of Lake Baikal to the Irkut river via the Kultuk vafley (Kononov and Mats 1986; Mats et al. 2000).

Publisher Summary The watershed of Lake Baikal constitutes the southern portion of the Siberian taiga and the northern part of the Mongolian steppe, and it is located at a high-latitude (51–56 N), far from the ocean. The paleoclimatic history of the Baikal region sensitively reflects past global changes, such as warm-cold and dry-moist oscillations of climate. Paleovegetational reconstruction of the region is indispensable to understanding how the Siberian taiga forest responded in timing and magnitude to past global changes. However, there are few palynological studies for paleovegetational reconstruction of the past million years in the region. This chapter presents a palynological study on the BDP96 Hole 1 core drilled by a Russian scientific drilling team in 1996. The results obtained in this study prove that the forest-desert alternations are closely related to global glacial–interglacial cycles during the Pleistocene. Considerable forest retreats are visible for relatively long periods during the late Pliocene, and a remarkable desert prevailing period during the early and middle Pliocene preceded the forest dominant period. The work in the Baikal area has also shown that these forest-desert alternations are more sensitive to global paleoclimate changes than those found in other continental region records.

Publisher Summary This chapter describes the geology and vegetation around the study sites and the regional vegetation history in the southeastern and eastern coastal areas of Lake Baikal. Various paleoecological studies of mire sediments from the coastal areas of Lake Baikal were conducted and sediment samples from the last glacial and the Holocene are taken from eight bogs and two outcrops of peat sediment on the southeastern and eastern coasts of Lake Baikal and examined for fossil pollen, plant macrofossils, and charcoal fragments. The chronology of each deposit is based on radiocarbon dating. The results of these studies reveal the vegetation history of the taiga around Lake Baikal since the last glacial period. During the last interstade (approximately 35–30000 y BP), forests on the southeastern coast consisted mainly of spruce and birch, with Gramineae and Artemisia. Herbaceous plants such as Gramineae and Artemisia and shrubs such as willow, birch, and alder characterized the vegetation of the last glacial maximum. Between 12000 and 11000 y BP, spruce expanded again in the coastal areas. The changes in spruce suggest that the Lake Baikal area is a glacial refugia of dark coniferous taiga. In the early Holocene, the spruce was replaced by fir and pine on the southeastern coast. On the eastern coast, the forests contained both spruce and fir. Diploxylon and Haploxylon pine forests shared large areas with birch since 6000 y BP. In some sites on the southeastern coast, the concentration of charcoal fragments, which indicates fires, increases sharply in the upper sediments. This increase in charcoal probably reflects forest fires caused by human activity.

The Lake Baikal sediment is one of the best archives which records the Late Quaternary paleoclimatic changes at high-latitude inland of Asian continent. On the other hand, basin-fill sediment of the Kathmandu Valley is ideal for studying the history of Indian monsoon activities. We tried to reconstruct paleovegetation and paleoclimate changes in both regions during Late Quaternary based on palynological studies.